1. Field of the Invention
This invention relates to a double glazing glass, particularly to a double glazing glass using a polycarbonate sheet, possessing a high sealing property in the joined part and, therefore, having no possibility of forming dew in the internal cavity thereof.
2. Description of the Prior Art
The double glazing glass produced by superposing two glass sheets one on top of the other has been known to the art. The conventional double glazing glass is obtained, as illustrated in FIG. 3 (plan view) and FIG. 4 (cross section taken through FIG. 3 along the line IV--IV), by superposing two glass sheets 11, 12 through the medium of spacers 13 disposed along the four edges of the glass sheets, joining the spacers 13 and the glass sheets 11, 12 with a primary sealant 14 and filling the grooves formed on the outer sides of the spacers 13 and between the joined glass sheets with a secondary sealant 15. A total of four linear spacers 13 is disposed along the four opposed edges of the superposed glass sheets. The corner parts of the intervening space between the superposed glass sheets are fixed by connecting the terminal parts of the spacers 13 with a corner key 16. The spacer 13 is each a hollow member provided on the inner peripheral side thereof with an aperture 13A. The hollow part of each of the spacers is generally filled with a desiccant 17.
This sealing method for the double glazing glass which is described above is called the "dual-seal method" and is a part of leading methods currently available for sealing the double glazing glass. The primary sealant 14 is made of butyl rubber and the secondary sealant 15 is made of a polysulfide or silicone type (acetic acid type) compound. The spacers 13 are made prevalently of an aluminum substance.
Incidentally, a polycarbonate sheet possesses conspicuously high impact resistance, excels in crack resistance and penetration resistance, and exhibits high safety as compared with a glass sheet and, as such, has been attracting attention as an ideal substitute for the glass sheet. Studies are now under way in search of a feasible double glazing glass using a polycarbonate sheet.
The adhesiveness of the polycarbonate sheet, however, has so far discouraged major glass manufactures from commercializing a double glazing glass using a polycarbonate sheet. Though double glazing glasses of this sort are being produced nominally, they are deficient in durability and other properties.
When a double glazing glass is constructed by the "dual-seal method" using a polycarbonate sheet as illustrated in FIG. 3 and FIG. 4, the primary sealant of butyl rubber manifests its sealing effect, whereas the second sealant which is generally made of a polysulfide type or silicone type(acetic acid type) compound defies adhesion to the polycarbonate sheet. The produced double glazing glass, therefore, encounters interfacial separation between the polycarbonate sheet and the second sealant. Though the idea of subjecting the polycarbonate sheet to a primer treatment for the purpose of imparting improved adhesiveness to the polycarbonate sheet is conceivable, the application of the primer treatment to the polycarbonate sheet is infeasible because the polycarbonate sheet is cracked by the solvent used in the treatment.
The currently available double glazing glasses using a polycarbonate sheet, therefore, rely for adhesion of the component sheets substantially upon the primary sealant. When any of the sealed parts using this primary sealant is injured, the part is no longer capable of sealing the double glazing glass and the air space formed in the inner cavity admits moisture and suffers formation of dew on the inner sheet surfaces. Further, because the spacers and the corner keys are separate articles, it naturally follows that gaps occur therebetween. Since the secondary sealant has only an insufficient sealing property, the moisture from the ambient air finds its way into the air space in the inner cavity through the gap. Again, this moisture possibly forms dew on the inner sheet surfaces.